A GENOMIC REGION FROM PSEUDOMONAS-FLUORESCENS PF-5 REQUIRED FOR PYRROLNITRIN PRODUCTION AND INHIBITION OF PYRENOPHORA-TRITICI-REPENTIS IN WHEAT-STRAW

Pseudomonas fluorescens strain Pf-5, which produces many antifungal me tabolites including pyrrolnitrin, inhibited mycelial growth of Pyrenop hora tritici-repentis in agar culture and suppressed ascocarp formatio n by the fungus on axenically infested wheat straw kept moist during i ncubation. Purified pyrrolnitrin was similarly inhibitory. A Tn5 mutan t of Pf-5 that did not produce detectable levels of pyrrolnitrin did n ot inhibit P. tritici-repentis on a culture medium or on wheat straw. A genomic region of Pf-5 was cloned that restored the pyrrolnitrin-def icient Tn5 mutant to pyrrolnitrin production and antagonism to P. trit ici-repentis in culture. Pf-5 did not persist or suppress P. tritici-r epentis on naturally infested wheat straw incubated under simulated fi eld conditions of fluctuating moist and dry periods.